>At the beginning of UT, the search was against all messages. When the total number of messages got huge, we had long discussions on how to make it faster and easier for the user. Michel came with the current solution and, (at least in my opinion), this is good more often than bad.

Limiting the search time is a laudable goal. There are a couple of things that would preserve this concept while mitigating the inconvenience of manually selecting a search time frame.

(1) If a search in the most recent time frame fails, proceed to the next older frame (and so on) until you find at least one match (or, having searched all timeframes) the search fails for all time frames.

(2) Not sure if the original reason for limiting time frames was to limit server load or to improve response time for for the user doing the search. If the latter, then allowing the user finer control of the timeframe bounds is a possibility. If the former, UT's current solution seems optimum, though I'd probably make the primary category be 'The last six months' rather than the 'last half calendar year' since the latter filter reduces the default search timeframe to a relatively small number of messages depending on what time of the year you actually do the search.